System and method for downlink and uplink control channel communication

ABSTRACT

A terminal device capable of providing a method for determining PUCCH resources used for notification of response signals indicating error detection results for downlink line data, when ARQ is applied during communications using an uplink unit band and a plurality of downlink unit bands associated to the uplink unit band and when downlink data allocations are instructed using an ePDCCH. In this device, a control unit ( 208 ) determines A/N resources on the basis of whether a channel used for transmitting downlink control information (DCI) is a PDCCH or an ePDCCH.

TECHNICAL FIELD

The present invention relates to a terminal apparatus, a base stationapparatus and a transmission and reception method.

BACKGROUND ART

3GPP LTE employs Orthogonal Frequency Division Multiple Access (OFDMA)as a downlink communication scheme. In radio communication systems towhich 3GPP LTE is applied, base stations transmit synchronizationsignals (i.e., Synchronization Channel: SCH) and broadcast signals(i.e., Broadcast Channel: BCH) using predetermined communicationresources. Meanwhile, each terminal finds an SCH first and therebyensures synchronization with a base station. Subsequently, the terminalreads BCH information to acquire base station-specific parameters suchas a frequency bandwidth (see, Non-Patent Literature (hereinafter,abbreviated as NPL) 1, 2 and 3).

In addition, upon completion of the acquisition of the basestation-specific parameters, each terminal performs a connection requestto the base station to thereby establish a communication link with thebase station. The base station transmits control information via adownlink control channel such as Physical Downlink Control CHannel(PDCCH) as appropriate to the terminal with which a communication linkhas been established.

The terminal performs “blind-determination” on each of a plurality ofcontrol information items included in the received PDCCH (i.e., Downlink(DL) Assignment Control Information: also referred to as DownlinkControl Information (DCI)). Specifically, each of the controlinformation items includes a Cyclic Redundancy Check (CRC) part and thebase station masks this CRC part using the terminal ID of thetransmission target terminal. Accordingly, until the terminal demasksthe CRC part of the received control information item with its ownterminal ID, the terminal cannot determine whether or not the controlinformation item is intended for the terminal. In thisblind-determination, if the result of demasking the CRC part indicatesthat the CRC operation is OK, the control information item is determinedas being intended for the terminal.

Moreover, in 3GPP LTE, Automatic Repeat Request (ARQ) is applied todownlink data to terminals from a base station. Specifically, eachterminal feeds back response signals indicating the result of errordetection on the downlink data to the base station. Each terminalperforms a CRC on the downlink data and feeds back Acknowledgment (ACK)when CRC=OK (no error) or Negative Acknowledgment (NACK) when CRC=Not OK(error) to the base station as response signals. An uplink controlchannel such as Physical Uplink Control Channel (PUCCH) is used to feedback the response signals (i.e., ACK/NACK signals (hereinafter, may bereferred to as “A/N,” simply)).

The control information to be transmitted from a base station hereinincludes resource assignment information including information onresources assigned to the terminal by the base station. As describedabove, PDCCH is used to transmit this control information. The PDCCHincludes one or more L1/L2 control channels (L1/L2 CCH). Each L1/L2 CCHconsists of one or more Control Channel Elements (CCE). Morespecifically, a CCE is the basic unit used to map the controlinformation to PDCCH. Moreover, when a single L1/L2 CCH consists of aplurality of CCEs (2, 4 or 8), a plurality of contiguous CCEs startingfrom a CCE having an even index are assigned to the L1/L2 CCH. The basestation assigns the L1/L2 CCH to the resource assignment target terminalin accordance with the number of CCEs required for reporting the controlinformation to the resource assignment target terminal. The base stationmaps the control information to physical resources corresponding to theCCEs of the L1/L2 CCH and transmits the mapped control information.

In addition, CCEs are associated with component resources of PUCCH(hereinafter, may be referred to as “PUCCH resource”) in a one-to-onecorrespondence. Accordingly, a terminal that has received an L1/L2 CCHidentifies the component resources of PUCCH that correspond to the CCEsforming the L1/L2 CCH and transmits response signals to the base stationusing the identified resources. However, when the L1/L2 CCH occupies aplurality of contiguous CCEs, the terminal transmits the responsesignals to the base station using a PUCCH component resourcecorresponding to a CCE having a smallest index among the plurality ofPUCCH component resources respectively corresponding to the plurality ofCCEs (i.e., PUCCH component resource associated with a CCE having aneven numbered CCE index). In this manner, the downlink communicationresources are efficiently used.

As illustrated in FIG. 1, a plurality of response signals transmittedfrom a plurality of terminals are spread using a Zero Auto-correlation(ZAC) sequence having the characteristic of zero autocorrelation intime-domain, a Walsh sequence and a discrete Fourier transform (DFT)sequence, and are code-multiplexed in a PUCCH. In FIG. 1, (W₀, W₁, W₂,W₃) represent a length-4 Walsh sequence and (F₀, F₀, F₂) represent alength-3 DFT sequence. As illustrated in FIG. 1, ACK or NACK responsesignals are primary-spread over frequency components corresponding to 1SC-FDMA symbol by a ZAC sequence (length-12) in frequency-domain. Morespecifically, the length-12 ZAC sequence is multiplied by a responsesignal component represented by a complex number. Subsequently, the ZACsequence serving as the response signals and reference signals after theprimary-spread is secondary-spread in association with each of a Walshsequence (length-4: W₀-W₃ (may be referred to as Walsh Code Sequence))and a DFT sequence (length-3: F₀-F₂). To put it more specifically, eachcomponent of the signals of length-12 (i.e., response signals afterprimary-spread or ZAC sequence serving as reference signals (i.e.,Reference Signal Sequence)) is multiplied by each component of anorthogonal code sequence (i.e., orthogonal sequence: Walsh sequence orDFT sequence). Moreover, the secondary-spread signals are transformedinto signals of length-12 in the time-domain by inverse fast Fouriertransform (IFFT). A CP is added to each signal obtained by IFFTprocessing, and the signals of one slot consisting of seven SC-FDMAsymbols are thus formed.

The response signals from different terminals are spread using ZACsequences each corresponding to a different cyclic shift value (i.e.,index) or orthogonal code sequences each corresponding to a differentsequence number (i.e., orthogonal cover index (OC index)). An orthogonalcode sequence is a combination of a Walsh sequence and a DFT sequence.In addition, an orthogonal code sequence is referred to as a block-wisespreading code in some cases. Thus, base stations can demultiplex thecode-multiplexed plurality of response signals using the related artdespreading and correlation processing (see, NPL 4).

However, it is not necessarily true that each terminal succeeds inreceiving downlink assignment control signals because the terminalperforms blind-determination in each subframe to find downlinkassignment control signals intended for the terminal. When the terminalfails to receive the downlink assignment control signals intended forthe terminal on a certain downlink component carrier, the terminal wouldnot even know whether or not there is downlink data intended for theterminal on the downlink component carrier. Accordingly, when a terminalfails to receive the downlink assignment control signals intended forthe terminal on a certain downlink component carrier, the terminalgenerates no response signals for the downlink data on the downlinkcomponent carrier. This error case is defined as discontinuoustransmission of ACK/NACK signals (DTX of response signals) in the sensethat the terminal transmits no response signals.

In 3GPP LTE systems (may be referred to as “LTE system,” hereinafter),base stations assign resources to uplink data and downlink data,independently. For this reason, in the 3GPP LTE system, terminals (i.e.,terminals compliant with LTE system (hereinafter, referred to as “LTEterminal”)) encounter a situation where the terminals need to transmituplink data and response signals for downlink data simultaneously in theuplink. In this situation, the response signals and uplink data from theterminals are transmitted using time-division multiplexing (TDM). Asdescribed above, the single carrier properties of transmission waveformsof the terminals are maintained by the simultaneous transmission ofresponse signals and uplink data using TDM.

In addition, as illustrated in FIG. 2, the response signals (i.e.,“A/N”) transmitted from each terminal partially occupy the resourcesassigned to uplink data (i.e., Physical Uplink Shared CHannel (PUSCH)resources) (i.e., response signals occupy some SC-FDMA symbols adjacentto SC-FDMA symbols to which reference signals (RS) are mapped) and arethereby transmitted to a base station in time-division multiplexing(TDM). In FIG. 2, “subcarriers” in the vertical axis of the drawing arealso termed as “virtual subcarriers” or “time contiguous signals,” and“time contiguous signals” that are collectively inputted to a discreteFourier transform (DFT) circuit in a SC-FDMA transmitter are representedas “subcarriers” for convenience. More specifically, optional data ofthe uplink data is punctured due to the response signals in the PUSCHresources. Accordingly, the quality of uplink data (e.g., coding gain)is significantly reduced due to the punctured bits of the coded uplinkdata. For this reason, base stations instruct the terminals to use avery low coding rate and/or to use very large transmission power so asto compensate for the reduced quality of the uplink data due to thepuncturing.

Meanwhile, the standardization of 3GPP LTE-Advanced for realizing fastercommunications than 3GPP LTE is in progress. 3GPP LTE-Advanced systems(may be referred to as “LTE-A system,” hereinafter) follow LTE systems.3GPP LTE-Advanced introduces base stations and terminals capable ofcommunicating with each other using a wideband frequency of 40 MHz orgreater to realize a downlink transmission rate up to 1 Gbps or above.

In the LTE-A system, in order to simultaneously achieve backwardcompatibility with the LTE system and ultra-high-speed communicationsseveral times faster than transmission rates in the LTE system, theLTE-A system band is divided into “component carriers” of 20 MHz orbelow, which is the bandwidth supported by the LTE system. In otherwords, the “component carrier” is defined herein as a band having amaximum width of 20 MHz and as the basic unit of communication band.Moreover, in FDD (frequency division duplex) systems, “componentcarrier” in downlink (hereinafter, referred to as “downlink componentcarrier”) is defined as a band obtained by dividing a band according todownlink frequency band information in a BCH broadcasted from a basestation or as a band defined by a distribution width when a downlinkcontrol channel (PDCCH) is distributed in the frequency domain. Inaddition, “component carrier” in uplink (hereinafter, referred to as“uplink component carrier”) may be defined as a band obtained bydividing a band according to uplink frequency band information in a BCHbroadcasted from a base station or as the basic unit of a communicationband of 20 MHz or below including a Physical Uplink Shared CHannel(PUSCH) in the vicinity of the center of the band and PUCCHs for LTE onboth ends of the band. Note that the term “component carrier” may bealso referred to as “cell” in English in 3GPP LTE-Advanced. In addition,“component carrier” may be also abbreviated as CC(s).

The LTE-A system supports communication using a band obtained bybundling several component carriers, so-called carrier aggregation (CA).Note that while a UL-DL configuration can be set for each componentcarrier, an LTE-A system compliant terminal (hereinafter, referred to as“LTE-A terminal”) is designed on the assumption that the same UL-DLconfiguration is set among a plurality of component carriers.

FIGS. 3A and 3B are diagrams provided for describing asymmetric carrieraggregation and a control sequence applied to individual terminals.

As illustrated in FIG. 3B, a configuration in which carrier aggregationis performed using two downlink component carriers and one uplinkcomponent carrier on the left is set for terminal 1, while aconfiguration in which the two downlink component carriers identicalwith those used by terminal 1 are used but uplink component carrier onthe right is used for uplink communications is set for terminal 2.

Referring to terminal 1, a base station (that is, LTE-A system compliantbase station (hereinafter, referred to as “LTE-A base station”)) and anLTE-A terminal included in the LTE-A system transmit and receive signalsto and from each other in accordance with the sequence diagramillustrated in FIG. 3A. As illustrated in FIG. 3A, (1) terminal 1 issynchronized with the downlink component carrier on the left whenstarting communications with the base station and reads information onthe uplink component carrier paired with the downlink component carrieron the left from a broadcast signal called system information block type2 (SIB2). (2) Using this uplink component carrier, terminal 1 startscommunications with the base station by transmitting, for example, aconnection request to the base station. (3) Upon determining that aplurality of downlink component carriers need to be assigned to theterminal, the base station instructs the terminal to add a downlinkcomponent carrier. However, in this case, the number of uplink componentcarriers is not increased, and terminal 1, which is an individualterminal, starts asymmetric carrier aggregation.

In addition, in the LTE-A system to which carrier aggregation isapplied, a terminal may receive a plurality of downlink data items on aplurality of downlink component carriers at a time. In LTE-A, studieshave been carried out on channel selection (also referred to as“multiplexing”), bundling and a discrete Fourier transform spreadorthogonal frequency division multiplexing (DFT-S-OFDM) format (may alsobe referred to as “PUCCH Format 3”) as a method of transmitting aplurality of response signals for the plurality of downlink data items.In channel selection, a terminal causes not only symbol points used forresponse signals, but also the resources to which the response signalsare mapped to vary in accordance with the pattern for results of theerror detection on the plurality of downlink data items. Compared withchannel selection, in bundling, a terminal bundles ACK or NACK signalsgenerated according to the results of error detection on the pluralityof downlink data items (i.e., bundles by calculating a logical AND ofthe results of error detection on the plurality of downlink data items,provided that ACK=1 and NACK=0), and transmits response signals usingone predetermine resource (see NPLs 6 and 7). In transmission using theDFT-S-OFDM format (PUCCH Format 3), a terminal jointly encodes (i.e.,joint coding) the response signals for the plurality of downlink dataitems and transmits the coded data using the format (see, NPL 5). Forexample, a terminal may feed back the response signals (i.e., ACK/NACK)using channel selection, bundling or DFT-S-OFDM according to the numberof bits for a pattern for results of error detection. Alternatively, abase station may previously configure the method of transmitting theresponse signals.

Furthermore, as shown in FIG. 4, the terminal transmits response signalsusing one of a plurality of component carriers. A component carrier thattransmits such response signals is called “primary component carrier(PCC)” or “primary cell (PCell).” A component carrier other than theprimary component carrier is called “secondary component carrier (SCC)”or “secondary cell (SCell).” For example, the PCC (PCell) is a componentcarrier that transmits broadcast information on a component carrier thattransmits response signals (e.g., system information block type 1(SIB1)).

The following two methods are considered as a possible method oftransmitting response signals in uplink when a terminal receivesdownlink assignment control information via a PDCCH and receivesdownlink data.

One is a method to transmit response signals using a PUCCH resourceassociated in a one-to-one correspondence with a beginning CCE indexn_(CCE) (or n_(CCE)+1 adjacent thereto) of a control channel element(CCE) occupied by the PDCCH (i.e., implicit signaling) (hereinafter,method 1). More specifically, when DCI intended for a terminal served bya base station is allocated in a PDCCH region, each PDCCH occupies aresource consisting of one or a plurality of contiguous CCEs. Inaddition, as the number of CCEs occupied by a PDCCH (i.e., the number ofaggregated CCEs: CCE aggregation level), one of aggregation levels 1, 2,4 and 8 is selected according to the number of information bits of theassignment control information or a propagation path condition of theterminal, for example.

The other method is to previously report a PUCCH resource to eachterminal from a base station (i.e., explicit signaling) (hereinafter,method 2). To put it differently, each terminal transmits responsesignals using the PUCCH resource previously indicated by the basestation in method 2.

In method 2, PUCCH resources common to a plurality of terminals (e.g.,four PUCCH resources) may be previously indicated to the terminals froma base station. For example, terminals may employ a method to select onePUCCH resource to be actually used, on the basis of a transmit powercontrol (TPC) command of two bits included in DCI in SCell. In thiscase, the TPC command is called an ACK/NACK resource indicator (ARI).Such a TPC command allows a certain terminal to use an explicitlysignaled PUCCH resource in a certain frame while allowing anotherterminal to use the same explicitly signaled PUCCH resource in anothersubframe in the case of explicit signaling.

Regarding PUCCH Format 3 and channel selection, which are methods ofindicating results of error detection when carrier aggregation isapplied, a method of determining PUCCH resources will be described withreference to FIGS. 5A and 5B and FIGS. 6A and 6B.

In PUCCH Format 3, as shown in FIG. 5B, a terminal indicates results oferror detection corresponding to a plurality of downlink data items foreach downlink component carrier received in a maximum of five downlinkcomponent carriers to a base station using PUCCH Format 3 resources orPUCCH Format 1b resources. To be more specific, the base stationindicates a TPC command of PUCCH in a field including a 2-bit TPCcommand (also referred to as “TPC field”) with a PDCCH that specifiesthe PDSCH of PCell. That is, this field is not used as an ARI. The basestation indicates a PUCCH resource (PUCCH Format 1b resource) associatedin a one-to-one correspondence with the beginning CCE index n_(CCE) ofthe CCE occupied by the PDCCH. Moreover, the base station previouslysets four PUCCH resources (PUCCH Format 3 resources) for the terminaland indicates an ARI with 2 bits of the TPC field in the PDCCH thatspecifies the PDSCH of SCell. That is, this field is not used as a TPCcommand of PUCCH. Note that in FIG. 5B, the ARI included in the PDCCHthat specifies the PDSCH of SCell is referred to as ARI1 forconvenience. The terminal determines which resource of the previouslyset four PUCCH resources (PUCCH Format 3 resources) should be used forPUCCH transmission according to an ARI indicated by the PDCCH. Note thatthe base station indicates the same value to the terminal as the valueof the ARI included in the PDCCH specifying the PDSCHs of a plurality ofSCells. This allows the terminal to always determine a single PUCCHFormat 3 resource.

In PUCCH Format 3, when detecting a PDCCH specifying the PDSCH of atleast one SCell, the terminal indicates results of error detection (inthe FDD system, a maximum of 10 bits (=5 CCs×2 CWs)) to the base stationusing the above-described PUCCH Format 3 resources. On the other hand,when detecting only a PDCCH specifying the PDSCH of PCell, the terminalindicates results of error detection (a maximum of 2 bits (=1 CC×2 CWs))to the base station using a PUCCH Format 1b resource associated in aone-to-one correspondence with the beginning CCE index n_(CCE) of thePDCCH.

The PUCCH Format 1b resource is a PUCCH resource optimized fortransmission of results of error detection of up to a maximum of 2 bitsand can also be orthogonalized with a maximum of 48 resources. While thePUCCH Format 3 resource is a PUCCH resource optimized for transmissionof more results of error detection, it can orthogonalize only up to amaximum of 4 resources. When the number of bits of results of errordetection is small, using PUCCH resources optimized for a smaller numberof bits of results of error detection allows the PUCCH resources to beorthogonalized to more resources and thereby increases the utilizationefficiency of PUCCH resources. Moreover, required PUCCH transmissionpower at the terminal necessary to satisfy required quality in the basestation can also be reduced.

Furthermore, when detecting only a PDCCH that specifies a PDSCH ofPCell, the terminal indicates results of error detection to the basestation using a PUCCH Format 1b resource associated in a one-to-onecorrespondence with the beginning CCE index n_(CCE) of the PDCCH,whereby, results of error detection for at least PDSCH of PCell can beindicated without inconsistency between the base station and theterminal even for a period during which the understanding of the settingof the number of CCs differs between the base station and the terminal(hereinafter may be expressed as “supporting LTE fallback”).

To be more specific, there is a period during which the understanding ofthe number of CCs configured in the terminal differs between the basestation and the terminal (uncertainty period or misalignment period).The base station indicates, to the terminal, a message indicating areconfiguration so as to change the number of CCs (e.g., from 1 CC to 2CCs or vice versa) and, upon reception of the message, the terminalunderstands that the number of CCs has been changed and indicates, tothe base station, a message indicating completion of the reconfigurationof the number of CCs. The period in which the understanding about thenumber of CCs configured for a terminal is different between a basestation and the terminal stems from the fact that the base stationunderstands, upon reception of the message, for the first time, that thenumber of CCs configured for the terminal has been changed. In a casewhere the terminal detects only a PDCCH specifying the PDSCH of PCell incommon before and after the change of the number of CCs (e.g., FIG. 5Aand FIG. 5B or FIG. 6A and FIG. 6B), if the terminal operates so as touse a PUCCH Format 1b resource associated in a one-to-one correspondencewith the beginning CCE index n_(CCE) of the PDCCH, the terminal canindicate results of error detection for at least PDSCH of PCell to thebase station without inconsistency (that is, supporting LTE fallback)even for a period during which the understanding of the number of CCsdiffers.

In channel selection, as shown in FIG. 6B, the terminal indicatesresults of error detection corresponding to a plurality of downlink dataitems for each downlink component carrier received in a maximum of twodownlink component carriers to the base station using four PUCCH Format1b resources. In channel selection, not only symbol points used forresponse signals but also PUCCH Format 1b resources to which responsesignals are mapped are changed in accordance with a pattern (combinationof ACK/NACK) of the results of error detection regarding a plurality ofdownlink data items. In channel selection, the base station indicates aTPC command of PUCCH in a field including a 2-bit TPC command (alsoreferred to as “TPC field”) in a PDCCH of PCell. That is, this field isnot used as an ARI. The base station specifies the PUCCH resources(PUCCH Format 1b resources) associated in a one-to-one correspondencewith the beginning CCE index n_(CCE) of the CCE occupied by the PDCCHand CCE index n_(CCE)+1 adjacent thereto respectively (PUCCH resources 0and 1 in FIGS. 6A and 6B). The base station previously sets four PUCCHresource pairs (PUCCH Format 1b resource pairs) for the terminal andindicates an ARI using 2 bits of the TPC field in a PDCCH of SCell. Thatis, this field is not used as a TPC command of PUCCH. In FIGS. 6A and6B, an ARI included in a PDCCH of SCell is referred to as ARI1 forconvenience. The terminal determines one resource pair of the fourpreviously set PUCCH resource pairs (PUCCH Format 1b resource pairs)according to the ARI indicated by the PDCCH (PUCCH resources 2 and 3 inFIG. 6B).

In recent years, it has become common to transmit not only audio databut also large-volume data, such as still image data and moving imagedata in cellular mobile communication systems in response to spread ofmultimedia information. In LTE-Advanced (Long Term Evolution Advanced),studies are being actively conducted on achieving high transmissionrates using wide radio bands, multiple-input multiple-output (MIMO)transmission technique and interference control technique.

In consideration of the fact that various devices for M2M (machine tomachine) communication or the like are introduced as radio communicationterminals and the number of terminals multiplexed by a MIMO transmissiontechnique, there is concern about a shortage of resources in a region towhich PDCCH (Physical Downlink Control CHannel: downlink controlchannel) used for control signals are mapped (that is, “PDCCH region”).When control signals (PDCCHs) cannot be mapped due to this shortage ofresources, data cannot be assigned to terminals. For this reason, evenwhen there are resource regions available for data mapping, they cannotbe used, and the system throughput may decrease.

As a method of solving this shortage of resources, studies are beingcarried out on a possibility of arranging control signals intended forterminals served by the base station in PDSCH regions as well. Resourceregions in which control signals intended for terminals served by thebase station are mapped (resource regions available to both a controlchannel and a data channel) are called “enhanced PDCCH (ePDCCH)regions.” Thus, by mapping control signals in the data region (that is,ePDCCH), it is possible to achieve transmission power control overcontrol signals transmitted to terminals located in the vicinity of acell edge or control over interference provided with transmitted controlsignals to other cells or control over interference provided from theother cells to the own cell.

In LTE, DL assignment indicating downlink data assignment and UL grantindicating uplink data assignment are transmitted by PDCCHs.

In LTE-Advanced, DL assignment and UL grant are assigned to an ePDCCH aswell as PDCCH. Studies are being carried out on a possibility ofdividing resources to which DL assignment is mapped and resources towhich UL grant is mapped in an ePDCCH in the frequency domain.

Studies are being carried out on a possibility of “localized assignment”whereby ePDCCHs are collectively assigned at positions close to eachother in a frequency band and “distributed assignment” whereby ePDCCHsare assigned in a frequency band in a distributed manner, as ePDCCHassignment methods (e.g., see FIG. 7).

CITATION LIST Non-Patent Literature

NPL 1

-   3GPP TS 36.211 V10.4.0, “Physical Channels and Modulation (Release    10),” December 2011

NPL 2

-   3GPP TS 36.212 V10.5.0, “Multiplexing and channel coding (Release    10),” March 2012

NPL 3

3GPP TS 36.213 V10.5.0, “Physical layer procedures (Release 10),” March2012

NPL 4

-   Seigo Nakao, Tomofumi Takata, Daichi Imamura, and Katsuhiko    Hiramatsu, “Performance enhancement of E-UTRA uplink control channel    in fast fading environments,” Proceeding of IEEE VTC 2009 spring,    April. 2009

NPL 5

-   Ericsson and ST-Ericsson, “A/N transmission in the uplink for    carrier aggregation,” R1-100909, 3GPP TSG-RAN WG1 #60, February 2010

NPL 6

-   ZTE, 3GPP RANI meeting #57, R1-091702, “Uplink Control Channel    Design for LTE-Advanced,” May 2009

NPL 7

-   Panasonic, 3GPP RANI meeting #57, R1-091744, “UL ACK/NACK    transmission on PUCCH for Carrier aggregation,” May 2009

SUMMARY OF INVENTION Technical Problem

As described above, LTE-Advanced defines the method of determining PUCCHresources when indicating DL assignment (that is, PDCCH indicatingPDSCH) in a PDCCH region, whereas the method of determining PUCCHresources when indicating DL assignment in an ePDCCH region has not beendiscussed so far.

An object of the present invention is to provide a method of determininga PUCCH resource used to indicate a response signal indicating a resultof error detection on downlink data when ARQ is applied in communicationusing an uplink component carrier and a plurality of downlink componentcarriers associated with the uplink component carrier and when downlinkdata assignment is specified by an ePDCCH.

Solution to Problem

A terminal apparatus according to an aspect of the present invention isa terminal apparatus that communicates with a base station apparatususing a plurality of component carriers and that receives a downlinkcontrol signal in a first resource region usable for both a downlinkcontrol channel and a downlink data channel or a second resource regionusable for a downlink control channel, the terminal apparatus including:a downlink control signal detection section that detects a downlinkcontrol signal assigned to the first resource region or the secondresource region, for each of the component carriers; a receiving sectionthat receives downlink data items using the plurality of componentcarriers, respectively; an error detection section that detects an errorof each of the downlink data items; a generating section that generatesa response signals using a result of error detection on each of thedownlink data items, the result of error detection being obtained by theerror detection section; and a control section that transmits theresponse signal to the base station apparatus, in which the controlsection switches between resource regions of an uplink communicationcontrol channel for transmitting the response signal, in accordance withwhether the downlink control signal detection section detects thedownlink control signal in the first resource region or the secondresource region.

A transmission method according to an aspect of the present invention isa transmission method for a terminal apparatus that communicates with abase station apparatus using a plurality of component carriers and thatreceives a downlink control signal in a first resource region usable forboth a downlink control channel and a downlink data channel or a secondresource region usable for a downlink control channel, the transmissionmethod including: detecting a downlink control signal assigned to thefirst resource region or the second resource region, for each of thecomponent carriers; receiving downlink data items using the plurality ofcomponent carriers, respectively; detecting an error of each of thedownlink data items; generating a response signal using an obtainedresult of error detection on each of the downlink data items; andtransmitting the response signal to the base station apparatus, in whichswitching between resource regions of an uplink communication controlchannel for transmitting the response signal is performed in accordancewith whether the downlink control signal is detected in the firstresource region or the second resource region.

Advantageous Effects of Invention

According to the present invention, it is made possible to determine aPUCCH resource used to indicate a response signal indicating a result oferror detection on downlink data when ARQ is applied in communicationusing an uplink component carrier and a plurality of downlink componentcarriers associated with the uplink component carrier and when downlinkdata assignment is specified by an ePDCCH.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram illustrating a method of spreading response signalsand reference signals;

FIG. 2 is a diagram illustrating an operation related to a case whereTDM is applied to response signals and uplink data on PUSCH resources;

FIGS. 3A and 3B are diagrams provided for describing asymmetric carrieraggregation and a control sequence applied to individual terminals;

FIG. 4 is a diagram provided for describing a method of determiningPUCCH resources in carrier aggregation;

FIGS. 5A and 5B are diagrams illustrating a method of determining PUCCHresources in PUCCH Format 3 when DL assignment is indicated by PDCCH;

FIGS. 6A and 6B are diagrams illustrating a method of determining PUCCHresources in channel selection when DL assignment is indicated by PDCCH;

FIG. 7 is a diagram illustrating an example of a method of assigningePDCCHs;

FIG. 8 is a block diagram illustrating a main configuration of aterminal according to Embodiment 1 of the present invention;

FIG. 9 is a block diagram illustrating a configuration of a base stationaccording to Embodiment 1 of the present invention;

FIG. 10 is a block diagram illustrating a configuration of a terminalaccording to Embodiment 1 of the present invention;

FIGS. 11A and 11B are diagrams provided for describing a method ofdetermining PUCCH resources according to Embodiment 1 of the presentinvention;

FIGS. 12A and 12B are diagrams provided for describing a method ofdetermining PUCCH resources according to Embodiment 2 of the presentinvention;

FIGS. 13A to 13C are diagrams provided for describing operation whenPDCCH and ePDCCH are used in combination according to Embodiment 3 ofthe present invention;

FIGS. 14A to 14C are diagrams provided for describing a method ofdetermining PUCCH resources according to Embodiment 3 of the presentinvention;

FIGS. 15A to 15D are diagrams provided for describing operation whenPDCCH and ePDCCH are used in combination according to Embodiment 4 ofthe present invention; and

FIGS. 16A to 16D are diagrams provided for describing a method ofdetermining PUCCH resources according to Embodiment 4 of the presentinvention.

Hereinafter, embodiments of the present invention will be described indetail with reference to the accompanying drawings. Throughout theembodiments, the same elements are assigned the same reference numeralsand any duplicate description of the elements is omitted.

DESCRIPTION OF EMBODIMENTS Embodiment 1

FIG. 8 is a main configuration diagram of terminal 200 according to thepresent embodiment. Terminal 200 communicates with base station 100using a plurality of component carriers including a first componentcarrier and a second component carrier. In terminal 200, extractionsection 204 receives downlink data assignment in a PDCCH region orePDCCH region and downlink data items in a PDSCH region specified by thedownlink data assignment respectively using the plurality of componentcarriers. In addition, CRC section 211 detects an error of each downlinkdata item, response signal generating section 212 generates a responsesignal using results of error detection on each downlink data itemobtained in CRC section 211, and control section 208 transmits theresponse signal to base station 100. However, control section 208determines PUCCH resources used for transmission of response signalsbased on which one of the PDCCH region and ePDCCH region is used toreceive the downlink data assignment.

[Configuration of Base Station]

FIG. 9 is a block diagram illustrating a configuration of base station100 according to Embodiment 1 of the present invention. In FIG. 9, basestation 100 includes control section 101, control information generatingsection 102, coding section 103, modulation section 104, coding section105, data transmission controlling section 106, modulation section 107,mapping section 108, inverse fast Fourier transform (IFFT) section 109,CP adding section 110, radio transmitting section 111, radio receivingsection 112, CP removing section 113, PUCCH extracting section 114,despreading section 115, sequence control section 116, correlationprocessing section 117, A/N determining section 118, bundled A/Ndespreading section 119, inverse discrete Fourier transform (IDFT)section 120, bundled A/N determining section 121 and retransmissioncontrol signal generating section 122.

Control section 101 assigns a downlink resource for transmitting controlinformation (i.e., downlink control information assignment resource) anda downlink resource for transmitting downlink data (i.e., downlink dataassignment resource) for a resource assignment target terminal(hereinafter, referred to as “destination terminal” or simply“terminal”) 200. This resource assignment is performed in a downlinkcomponent carrier included in a component carrier group configured forresource assignment target terminal 200. In addition, the downlinkcontrol information assignment resource is selected from among theresources corresponding to downlink control channel (i.e., PDCCH orePDCCH) in each downlink component carrier. Moreover, the downlink dataassignment resource is selected from among the resources correspondingto downlink data channel (i.e., PDSCH) in each downlink componentcarrier. In addition, when there are a plurality of resource assignmenttarget terminals 200, control section 101 assigns different resources toresource assignment target terminals 200, respectively.

The downlink control information assignment resources are equivalent toL1/L2 CCH described above. More specifically, the downlink controlinformation assignment resources are each formed of one or a pluralityof CCEs.

Control section 101 determines the coding rate used for transmittingcontrol information to resource assignment target terminal 200. The datasize of the control information varies depending on the coding rate.Thus, control section 101 assigns a downlink control informationassignment resource having the number of CCEs that allows the controlinformation having this data size to be mapped to the resource.

Control section 101 outputs information on the downlink data assignmentresource to control information generating section 102. Moreover,control section 101 outputs information on the coding rate to codingsection 103. In addition, control section 101 determines and outputs thecoding rate of transmission data (i.e., downlink data) to coding section105. Moreover, control section 101 outputs information on the downlinkdata assignment resource and downlink control information assignmentresource to mapping section 108.

Control information generating section 102 generates and outputs controlinformation including the information on the downlink data assignmentresource to coding section 103. This control information is generatedfor each downlink component carrier. In addition, when there are aplurality of resource assignment target terminals 200, the controlinformation includes the terminal ID of each destination terminal 200 inorder to distinguish resource assignment target terminals 200 from oneanother. For example, the control information includes CRC bits maskedby the terminal ID of destination terminal 200. This control informationmay be referred to as “control information carrying downlink assignment”or “downlink control information (DCI).”

Coding section 103 encodes the control information using the coding ratereceived from control section 101 and outputs the coded controlinformation to modulation section 104.

Modulation section 104 modulates the coded control information andoutputs the resultant modulation signal to mapping section 108.

Coding section 105 uses the transmission data (i.e., downlink data) foreach destination terminal 200 and the coding rate information fromcontrol section 101 as input and encodes and outputs the transmissiondata to data transmission controlling section 106. However, when aplurality of downlink component carriers are assigned to destinationterminal 200, coding section 105 encodes each transmission data item tobe transmitted on a corresponding one of the downlink component carriersand outputs the coded transmission data item to data transmissioncontrolling section 106.

Data transmission controlling section 106 outputs the coded transmissiondata to modulation section 107 and also keeps the coded transmissiondata at the initial transmission. Data transmission controlling section106 keeps the coded transmission data for each destination terminal 200.In addition, data transmission controlling section 106 keeps thetransmission data for one destination terminal 200 for each downlinkcomponent carrier on which the transmission data is transmitted. Thus,it is possible to perform not only retransmission control for overalldata transmitted to destination terminal 200, but also retransmissioncontrol for data on each downlink component carrier.

Furthermore, upon reception of a NACK or DTX for downlink datatransmitted on a certain downlink component carrier from retransmissioncontrol signal generating section 122, data transmission controllingsection 106 outputs the data kept in the manner described above andcorresponding to this downlink component carrier to modulation section107. Upon reception of an ACK for the downlink data transmitted on acertain downlink component carrier from retransmission control signalgenerating section 122, data transmission controlling section 106deletes the data kept in the manner described above and corresponding tothis downlink component carrier.

Modulation section 107 modulates the coded transmission data receivedfrom data transmission controlling section 106 and outputs the resultantmodulation signals to mapping section 108.

Mapping section 108 maps the modulation signal of the controlinformation received from modulation section 104 to the resourceindicated by the downlink control information assignment resourcereceived from control section 101 and outputs the resultant modulationsignal to IFFT section 109.

Mapping section 108 maps the modulation signal of the transmission datareceived from modulation section 107 to the resource (i.e., PDSCH (i.e.,downlink data channel)) indicated by the downlink data assignmentresource received from control section 101 (i.e., information includedin the control information) and outputs the resultant modulation signalto IFFT section 109.

The control information and transmission data mapped to a plurality ofsubcarriers in a plurality of downlink component carriers in mappingsection 108 is transformed into time-domain signals fromfrequency-domain signals in IFFT section 109, and CP adding section 110adds a CP to the time-domain signals to form OFDM signals. The OFDMsignals undergo transmission processing such as digital to analog (D/A)conversion, amplification and up-conversion and/or the like in radiotransmitting section 111 and are transmitted to terminal 200 via anantenna.

Radio receiving section 112 receives, via an antenna, the uplinkresponse signal or reference signal transmitted from terminal 200, andperforms reception processing such as down-conversion, A/D conversionand/or the like on the uplink response signal or reference signal.

CP removing section 113 removes the CP added to the uplink responsesignal or reference signal from the uplink response signal or referencesignal that have undergone the reception processing.

PUCCH extracting section 114 extracts, from the PUCCH signal included inthe received signal, the signal in the PUCCH region corresponding to thebundled ACK/NACK resource previously indicated to terminal 200. Thebundled ACK/NACK resource herein refers to a resource used fortransmission of the bundled ACK/NACK signal and adopting the DFT-S-OFDMformat structure. More specifically, PUCCH extracting section 114extracts the data part of the PUCCH region corresponding to the bundledACK/NACK resource (i.e., SC-FDMA symbols on which the bundled ACK/NACKresource is assigned) and the reference signal part of the PUCCH region(i.e., SC-FDMA symbols on which the reference signals for demodulatingthe bundled ACK/NACK signals are assigned). PUCCH extracting section 114outputs the extracted data part to bundled A/N despreading section 119and outputs the extracted reference signal part to despreading section115-1.

In addition, PUCCH extracting section 114 extracts, from the PUCCHsignals included in the received signals, a plurality of PUCCH regionscorresponding to an A/N resource (or also referred to as “PUCCHresource”) associated with a CCE that has been occupied by the PDCCHused for transmission of the downlink assignment control information(DCI), and corresponding to a plurality of A/N resources previouslyindicated to terminal 200. The A/N resource herein refers to theresource to be used for transmission of an A/N. Moreover, PUCCHextracting section 114 determines an A/N resource based on whether thechannel used for transmission of the downlink assignment controlinformation (DCI) is PDCCH or ePDCCH. Details of the method ofdetermining A/N resources will be described later.

Furthermore, PUCCH extracting section 114 extracts the data part of thePUCCH region corresponding to the A/N resource (i.e., SC-FDMA symbols onwhich the uplink control signals are assigned) and the reference signalpart of the PUCCH region (i.e., SC-FDMA symbols on which the referencesignals for demodulating the uplink control signals are assigned). PUCCHextracting section 114 outputs both of the extracted data part andreference signal part to despreading section 115-2. In this manner, theresponse signal is received on the resource selected from the PUCCHresource associated with the CCE and the specific PUCCH resourcepreviously indicated to terminal 200.

Sequence control section 116 generates a base sequence (i.e., length-12ZAC sequence) that may be used for spreading each of the A/N indicatedfrom terminal 200, the reference signal for the A/N, and the referencesignal for the bundled ACK/NACK signals. In addition, sequence controlsection 116 identifies a correlation window corresponding to a resourceon which the reference signal may be assigned (hereinafter, referred toas “reference signal resource”) in PUCCH resources that may be used byterminal 200. Sequence control section 116 outputs the informationindicating the correlation window corresponding to the reference signalresource on which the reference signal may be assigned in bundledACK/NACK resource and the base sequence to correlation processingsection 117-1. Sequence control section 116 outputs the informationindicating the correlation window corresponding to the reference signalresource and the base sequence to correlation processing section 117-1.In addition, sequence controlling section 116 outputs the informationindicating the correlation window corresponding to the A/N resources onwhich an A/N and the reference signals for the A/N are assigned and thebase sequence to correlation processing section 117-2.

Despreading section 115-1 and correlation processing section 117-1perform processing on the reference signals extracted from the PUCCHregion corresponding to the bundled ACK/NACK resource.

More specifically, despreading section 115-1 despreads the referencesignal part using a Walsh sequence to be used in secondary-spreading forthe reference signals of the bundled ACK/NACK resource by terminal 200and outputs the despread signals to correlation processing section117-1.

Correlation processing section 117-1 uses the information indicating thecorrelation window corresponding to the reference signal resource andthe base sequence and thereby finds a correlation value between thesignals received from despreading section 115-1 and the base sequencethat may be used in primary-spreading in terminal 200. Correlationprocessing section 117-1 outputs the correlation value to bundled A/Ndetermining section 121.

Despreading section 115-2 and correlation processing section 117-2perform processing on the reference signals and A/Ns extracted from theplurality of PUCCH regions corresponding to the plurality of A/Nresources.

Specifically, despreading section 115-2 despreads the data part andreference signal part using a Walsh sequence and a DFT sequence to beused in secondary-spreading for the data part and reference signal partof each of the A/N resources by terminal 200, and outputs the despreadsignals to correlation processing section 117-2.

Correlation processing section 117-2 uses the information indicating thecorrelation window corresponding to each of the A/N resources and thebase sequence and thereby finds each correlation value between thesignal received from despreading section 115-2 and base sequences thatmay be used in primary-spreading by terminal 200. Correlation processingsection 117-2 outputs each correlation value to A/N determining section118.

A/N determining section 118 determines, on the basis of the plurality ofcorrelation values received from correlation processing section 117-2,which of the A/N resources is used to transmit the signals from terminal200 or none of the A/N resources is used. When determining that thesignals are transmitted using one of the A/N resources from terminal200, A/N determining section 118 performs coherent detection using acomponent corresponding to the reference signals and a componentcorresponding to the A/N and outputs the result of coherent detection toretransmission control signal generating section 122. Meanwhile, whendetermining that terminal 200 uses none of the A/N resources, A/Ndetermining section 118 outputs the determination result indicating thatnone of the A/N resources is used to retransmission control signalgenerating section 122.

Bundled A/N despreading section 119 despreads, using a DFT sequence, thebundled ACK/NACK signals corresponding to the data part of the bundledACK/NACK resource received from PUCCH extracting section 114 and outputsthe despread signals to IDFT section 120.

IDFT section 120 transforms the bundled ACK/NACK signals in thefrequency-domain received from bundled A/N despreading section 119 intotime-domain signals by IDFT processing and outputs the bundled ACK/NACKsignals in the time-domain to bundled A/N determining section 121.

Bundled A/N determining section 121 demodulates the bundled ACK/NACKsignals corresponding to the data part of the bundled ACK/NACK resourcereceived from IDFT section 120, using the reference signal informationon the bundled ACK/NACK signals that is received from correlationprocessing section 117-1. In addition, bundled A/N determination section121 decodes the demodulated bundled ACK/NACK signals and outputs theresult of decoding to retransmission control signal generating section122 as the bundled A/N information. However, when bundled A/Ndetermining section 121 thus determines that the correlation valuereceived from correlation processing section 117-1 is smaller than athreshold and that terminal 200 does not use any bundled A/N resource totransmit the signals, bundled A/N determining section 121 outputs theresult of determination to retransmission control signal generatingsection 122.

Retransmission control signal generating section 122 determines whetheror not to retransmit the data transmitted on the downlink componentcarrier (i.e., downlink data) on the basis of the information receivedfrom bundled A/N determining section 121, the information received fromA/N determining section 118 and the information indicating a groupnumber set to terminal 200, and generates a retransmission controlsignal based on the result of determination. Specifically, whendetermining that downlink data transmitted on a certain downlinkcomponent carrier needs to be retransmitted, retransmission controlsignal generating section 122 generates retransmission control signalsindicating a retransmission command for the downlink data and outputsthe retransmission control signal to data transmission controllingsection 106. In addition, when determining that the downlink datatransmitted on a certain downlink component carrier does not need to beretransmitted, retransmission control signal generating section 122generates a retransmission control signal indicating not to retransmitthe downlink data transmitted on the downlink component carrier andoutputs the retransmission control signal to data transmissioncontrolling section 106.

[Configuration of Terminal]

FIG. 10 is a block diagram illustrating a configuration of terminal 200according to Embodiment 1. In FIG. 10, terminal 200 includes radioreceiving section 201, CP removing section 202, fast Fourier transform(FFT) section 203, extraction section 204, demodulation section 205,decoding section 206, determination section 207, control section 208,demodulation section 209, decoding section 210, CRC section 211,response signal generating section 212, coding and modulation section213, primary-spreading sections 214-1 and 214-2, secondary-spreadingsections 215-1 and 215-2, DFT section 216, spreading section 217, IFFTsections 218-1, 218-2 and 218-3, CP adding sections 219-1, 219-2 and219-3, time-multiplexing section 220, selection section 221 and radiotransmitting section 222.

Radio receiving section 201 receives, via an antenna, OFDM signalstransmitted from base station 100 and performs reception processing suchas down-conversion, A/D conversion and/or the like on the received OFDMsignals. Note that, the received OFDM signals include PDSCH signalsassigned to a resource in PDSCH (i.e., downlink data), or downlinkcontrol signals assigned to a resource in PDCCH and downlink controlsignals assigned to a resource in ePDCCH.

CP removing section 202 removes a CP that has been added to the OFDMsignals from the OFDM signals that have undergone the receptionprocessing.

FFT section 203 transforms the received OFDM signals intofrequency-domain signals by FFT processing and outputs the resultantreceived signals to extraction section 204.

Extraction section 204 extracts, from the received signals to bereceived from FFT section 203, downlink control channel signals (i.e.,PDCCH or ePDCCH) in accordance with coding rate information to bereceived. Specifically, the number of CCEs (or eCCEs) forming a downlinkcontrol information assignment resource varies depending on the codingrate. Thus, extraction section 204 uses the number of CCEs thatcorresponds to the coding rate as units of extraction processing, andextracts downlink control channel signal. In addition, the downlinkcontrol channel signal is extracted for each downlink component carrier.The extracted downlink control channel signal is outputted todemodulation section 205.

Extraction section 204 extracts downlink data (i.e., downlink datachannel signal (i.e., PDSCH signal)) from the received signal on thebasis of information on the downlink data assignment resource intendedfor terminal 200 to be received from determination section 207 to bedescribed, hereinafter, and outputs the downlink data to demodulationsection 209. As described above, extraction section 204 receives thedownlink assignment control information (i.e., DCI) mapped to the PDCCHand receives the downlink data on the PDSCH.

Demodulation section 205 demodulates the downlink control channel signalreceived from extraction section 204 and outputs the obtained result ofdemodulation to decoding section 206.

Decoding section 206 decodes the result of demodulation received fromdemodulation section 205 in accordance with the received coding rateinformation and outputs the obtained result of decoding to determinationsection 207.

Determination section 207 performs blind-determination (i.e.,monitoring) to find out whether or not the control information includedin the result of decoding received from decoding section 206 is thecontrol information intended for terminal 200. This determination ismade in units of decoding results corresponding to the units ofextraction processing. For example, determination section 207 demasksthe CRC bits by the terminal ID of terminal 200 and determines thecontrol information resulted in CRC=OK (no error) as the controlinformation intended for terminal 200. Determination section 207 outputsinformation on the downlink data assignment resource intended forterminal 200, which is included in the control information intended forterminal 200, to extraction section 204.

In addition, when detecting the control information (i.e., downlinkassignment control information) intended for terminal 200, determinationsection 207 informs control section 208 that an ACK/NACK signal will begenerated (or is present). Moreover, when detecting the controlinformation intended for terminal 200 from the PDCCH region,determination section 207 outputs information on a CCE that has beenoccupied by the PDCCH to control section 208.

Control section 208 determines an A/N resource based on whether thechannel used for transmission of downlink assignment control information(DCI) is a PDCCH or ePDCCH. Details of the method of determining A/Nresources will be described later. Control section 208 identifies theA/N resource associated with the CCE on the basis of the information onthe CCE received from determination section 207. Control section 208outputs, to primary-spreading section 214-1, a base sequence and acyclic shift value corresponding to the A/N resource associated with theCCE or the A/N resource previously indicated by base station 100, andalso outputs a Walsh sequence and a DFT sequence corresponding to theA/N resource to secondary-spreading section 215-1. In addition, controlsection 208 outputs the frequency resource information on the A/Nresource to IFFT section 218-1.

Control section 208 determines an A/N resource based on whether thechannel used for transmission of the downlink assignment controlinformation (DCI) is a PDCCH or ePDCCH. Details of the method ofdetermining A/N resources will be described later.

When determining to transmit bundled ACK/NACK signals using a bundledACK/NACK resource, control section 208 outputs the base sequence andcyclic shift value corresponding to the reference signal part (i.e.,reference signal resource) of the bundled ACK/NACK resource previouslyindicated by base station 100 to primary-despreading section 214-2 andoutputs a Walsh sequence to secondary-despreading section 215-2. Inaddition, control section 208 outputs the frequency resource informationon the bundled ACK/NACK resource to IFFT section 218-2.

Control section 208 outputs a DFT sequence used for spreading the datapart of the bundled ACK/NACK resource to spreading section 217 andoutputs the frequency resource information on the bundled ACK/NACKresource to IFFT section 218-3.

Control section 208 selects the bundled ACK/NACK resource or the A/Nresource and instructs selection section 221 to output the selectedresource to radio transmitting section 222. Moreover, control section208 instructs response signal generating section 212 to generate thebundled ACK/NACK signals or the ACK/NACK signals in accordance with theselected resource.

Demodulation section 209 demodulates the downlink data received fromextraction section 204 and outputs the demodulated downlink data todecoding section 210. Decoding section 210 decodes the downlink datareceived from demodulation section 209 and outputs the decoded downlinkdata to CRC section 211.

CRC section 211 performs error detection on the decoded downlink datareceived from decoding section 210, for each downlink component carrierusing CRC and outputs an ACK when CRC=OK (no error) or outputs a NACKwhen CRC=Not OK (error) to response signal generating section 212.Moreover, CRC section 211 outputs the decoded downlink data as thereceived data when CRC=OK (no error).

Response signal generating section 212 generates a response signal onthe basis of the reception condition of downlink data (i.e., result oferror detection on downlink data) on each downlink component carrierreceived from CRC section 211 and information indicating the previouslyset group number. Specifically, when instructed to generate the bundledACK/NACK signal by control section 208, response signal generatingsection 212 generates the bundled ACK/NACK signal including the resultsof error detection for the respective component carriers as individualdata items. Meanwhile, when instructed to generate ACK/NACK signals bycontrol section 208, response signal generating section 212 generates anACK/NACK signal of one symbol. Response signal generating section 212outputs the generated response signal to coding and modulation section213.

Upon reception of the bundled ACK/NACK signal, coding and modulationsection 213 encodes and modulates the received bundled ACK/NACK signalto generate the modulation signal of 12 symbols and outputs themodulation signal to DFT section 216. In addition, upon reception of theACK/NACK signal of one symbol, coding and modulation section 213modulates the ACK/NACK signal and outputs the modulation signal toprimary-spreading section 214-1.

Primary-spreading sections 214-1 and 214-2 corresponding to the A/Nresource and the reference signal resource of bundled ACK/NACK resourcespread ACK/NACK signals or reference signals using a base sequencecorresponding to the resource, in accordance with an instruction fromcontrol section 208, and outputs the spread signals tosecondary-spreading sections 215-1 and 215-2.

Secondary-spreading sections 215-1 and 215-2 spread the receivedprimary-spread signals using a Walsh sequence or a DFT sequence inaccordance with an instruction from control section 208 and outputs thespread signals to IFFT sections 218-1 and 218-2.

DFT section 216 performs DFT processing on 12 time-series sets ofreceived bundled ACK/NACK signals to obtain 12 signal components in thefrequency-domain. DFT section 216 outputs the 12 signal components tospreading section 217.

Spreading section 217 spreads the 12 signal components received from DFTsection 216 using a DFT sequence indicated by control section 208 andoutputs the spread signal components to IFFT section 218-3.

IFFT sections 218-1, 218-2 and 218-3 perform IFFT processing on thereceived signals in association with the frequency positions where thesignals are to be allocated, based on an instruction from controlsection 208. Accordingly, the signals inputted to IFFT sections 218-1,218-2 and 218-3 (i.e., ACK/NACK signals, the reference signals of A/Nresource, the reference signals of bundled ACK/NACK resource and bundledACK/NACK signals) are transformed into time-domain signals.

CP adding sections 219-1, 219-2 and 219-3 add the same signals as thelast part of the signals obtained by IFFT processing to the beginning ofthe signals as a CP.

Time-multiplexing section 220 time-multiplexes, on the bundled ACK/NACKresource, the bundled ACK/NACK signal received from CP adding section219-3 (i.e., signal transmitted using the data part of the bundledACK/NACK resource) and the reference signal of the bundled ACK/NACKresource to be received from CP adding section 219-2, and outputs themultiplexed signal to selection section 221.

Selection section 221 selects one of the bundled ACK/NACK resourcereceived from time-multiplexing section 220 and the A/N resourcereceived from CP adding section 219-1 and outputs the signal assigned tothe selected resource to radio transmitting section 222.

Radio transmitting section 222 performs transmission processing such asD/A conversion, amplification and up-conversion and/or the like on thesignal received from selection section 221 and transmits the resultantsignal to base station 100 via an antenna.

[Operations of Base Station 100 and Terminal 200]

A description will be provided regarding operations of base station 100and terminal 200 each configured in the manner described above.

The method of determining PUCCH resources according to the presentembodiment will be described with reference to FIGS. 11A and 11B. Thepresent embodiment will describe a method of determining PUCCH resourcesin a case where terminal 200 does not configure carrier aggregation(FIG. 11A) and in a case where terminal 200 configures carrieraggregation and PUCCH Format 3 (FIG. 11B) when DL assignment isindicated by ePDCCH.

In PUCCH Format 3 of the present embodiment, results of error detectioncorresponding to a plurality of downlink data items for each downlinkcomponent carrier received on a maximum of 5 downlink component carriersare indicated to base station 100 using PUCCH Format 3 resources orPUCCH Format 1b resources as shown FIG. 11B. To be more specific, basestation 100 indicates ARI (ARI3) in the TPC field by the ePDCCHspecifying the PDSCH of PCell. Terminal 200 determines which resource ofthe four previously set PUCCH resources (PUCCH Format 1b resources) isto be used for PUCCH transmission according to the ARI indicated by theePDCCH. On the other hand, base station 100 indicates the ARI (ARI2) inthe TPC field by the ePDCCH specifying the PDSCH of SCell. Terminal 200determines which resource of the four previously set PUCCH resources(PUCCH Format 3 resources) is to be used for PUCCH transmissionaccording to the ARI indicated by the ePDCCH.

In PUCCH Format 3 according to the present embodiment, when the terminaldetects an ePDCCH specifying the PDSCH of at least one SCell as in thecase of the operation using PDCCH, results of error detection areindicated to base station 100 using the above PUCCH Format 3 resources.On the other hand, when the terminal detects only the ePDCCH specifyingthe PDSCH of PCell, results of error detection are indicated to basestation 100 using the above PUCCH Format 1b resources.

The PUCCH Format 1b resource is a PUCCH resource optimized fortransmission of results of error detection of up to a maximum of 2 bitsand can be orthogonalized with a maximum of 48 resources. While thePUCCH Format 3 resource is a PUCCH resource optimized for transmissionof more results of error detection, the PUCCH Format 3 can beorthogonalized with only up to a maximum of 4 resources. Therefore,according to the present embodiment, when the number of bits of resultsof error detection is small as in the case of the operation using PDCCH,using PUCCH resources optimized to the number of bits of a fewer resultsof error detection allows the PUCCH resources to be orthogonalized withmore resources and can increase the utilization efficiency of the PUCCHresources. Furthermore, PUCCH transmission power in the terminalnecessary to satisfy required quality in the base station can bereduced.

According to the present embodiment, the method of determining a PUCCHformat used by ePDCCH is the same as the operation using a PDCCH. Thatis, when the terminal detects a PDCCH or ePDCCH specifying the PDSCH ofat least one SCell, the terminal indicates results of error detection tothe base station using PUCCH Format 3. On the other hand, when detectingonly one of PDCCH and ePDCCH specifying the PDSCH of PCell, the terminalindicates results of error detection to the base station using PUCCHFormat 1b. The method of generating response signals from results oferror detection for each PDSCH differs only depending on the PUCCHformat (that is, PUCCH Format 3 or PUCCH Format 1b). In PUCCH Format 3,response signals of a maximum of 10 bits (=5 CCs×2 CWs) are generated bycombining the respective results of error detection, whereas in PUCCHFormat 1b, response signals of a maximum of 2 bits (=1 CC×2 CWs) aregenerated by combining results of error detection of the PDSCH of PCell.For this reason, the processing involved in the generation of responsesignals can be commonly used for the operation using PDCCH and theoperation using ePDCCH. In other words, whether PDSCH is specified by aPDCCH or ePDCCH has nothing to do with processing of generating responsesignals, and it is the presence or absence of assignment of PDSCH ineach cell that has to do with the processing of generating responsesignals. This makes it possible to simplify the configurations of theterminal and the base station.

Embodiment 2

As in the case of Embodiment 1, in the present embodiment, a descriptionwill be given of a method of indicating PUCCH resources in a case whereDL assignment is indicated by ePDCCH when terminal 200 does not setcarrier aggregation and when terminal 200 sets carrier aggregation andPUCCH Format 3. The difference from Embodiment 1 lies in ARI (ARI3)specified by the ePDCCH that specifies the PDSCH of PCell and PUCCHresources specified by the ARI.

When carrier aggregation is set in a heterogeneous network environment(HetNet) that combines a cell having a large cell coverage and a cellhaving a small cell coverage, operating the cell having a large cellcoverage as PCell and the cell having a small cell coverage as SCell maybe possibly adopted to secure mobility of terminals. In carrieraggregation in such a HetNet environment, a base station covering anSCell is generally located closer to the terminal than a base stationcovering a PCell. Therefore, it is advantageous for the base stationcovering an SCell to perform downlink data communication with theterminal in terms of transmission power. For this reason, in carrieraggregation in a HetNet environment, only PCell performs downlink dataassignment less frequently. Thus, in the present embodiment, the ARI(ARI3) specified by the ePDCCH that specifies the PDSCH of PCellspecifies the same PUCCH resources (PUCCH Format 3 resources) as the ARI(ARI2) specified by the ePDCCH that specifies the PDSCH of SCell.

More specifically, the method of determining PUCCH resources accordingto the present embodiment will be described with reference to FIGS. 12Aand 12B. As shown in FIG. 12B, when carrier aggregation is set, basestation 100 indicates the ARI (ARI3) in a TPC field by ePDCCH thatspecifies the PDSCH of PCell. On the other hand, base station 100recognizes that the ARI (ARI2) is indicated to the TPC field by ePDCCHthat instructs PDSCH of SCell and operates accordingly. In the presentembodiment, base station 100 and terminal 200 always use ARI2 and ARI3as having the same value. Moreover, four previously set PUCCH resourcesare common so that PUCCH resources indicated by ARI2 and ARI3 are alsoidentical. Terminal 200 determines which one of the four previously setPUCCH resources (PUCCH Format 3 resources) is to be used for PUCCHtransmission according to ARI2 and ARI3.

On the other hand, as shown in FIG. 12A, when no carrier aggregation isset, base station 100 indicates ARI (ARI3) in the TPC field by theePDCCH that specifies the PDSCH of PCell. Terminal 200 determines whichone of the four previously set PUCCH resources (PUCCH Format 1bresources) is to be used for PUCCH transmission according to the ARIindicated by the ePDCCH.

As described so far, according to the present embodiment, when carrieraggregation is set, the terminal always transmits a response signalusing a PUCCH Format 3 resource, focusing on the fact that PDSCH is lessfrequently assigned only to PCell. ARI2 and ARI3 are always used ashaving the same value. Moreover, the four previously set PUCCH resourcesare made common so that the PUCCH resources indicated by ARI2 and ARI3also become identical. When no carrier aggregation is set, the terminaltransmits response signals using PUCCH Format 1b resources which arePUCCH resources optimized to the number of bits of a fewer results oferror detection.

Furthermore, when carrier aggregation is set, always using PUCCH Format3 resources eliminates the necessity for using PUCCH Format 1b resourceswhen the terminal fails to receive the ePDCCH that specifies the PDSCHof SCell although the base station has assigned both the PDSCHs of PCelland SCell. Therefore, the base station need not secure PUCCH Format 1bresources in preparation for a failure of the terminal to receive theePDCCH that specifies the PDSCH of SCell and can thereby reduce thePUCCH overhead.

Note that when carrier aggregation is set, if the PDSCH is assigned onlyto PCell, PUCCH Format 1b resources may be used which are PUCCHresources optimized to the number of bits of a fewer results of errordetection in the same way as when carrier aggregation is not set byspecifying the PDSCH not by ePDCCH but by PDCCH.

Embodiment 3

Embodiments 1 and 2 have described the method of indicating PUCCHresources when an ePDCCH is used. In actual operations, a PDCCH andePDCCH may be used in combination in units of cells or subframes.Furthermore, an operation using a cell without PDCCH (a cell that doesnot support backward compatibility) may also be possible. An operationusing a cell that does not support ePDCCH may also be possible. Thus,the present embodiment will show a method of indicating PUCCH resourceswhen a PDCCH and ePDCCH are used in combination in units of cells, inthe case of carrier aggregation is set according to Embodiment 2.

In the present embodiment, as shown in FIG. 13A, PDCCH and ePDCCH areused in combination in units of cells or subframes. For example, insubframe #0 (SF #0) in FIG. 13A, base station 100 specifies the PDSCHusing the PDCCH in PCell, SCell1 and SCell2, and specifies the PDSCHusing the ePDCCH in SCell3 and SCell4. FIG. 13B shows the method ofdetermining PUCCH resources in subframe #0 in FIG. 13A and FIG. 13Cshows the method of determining PUCCH resources in subframe #1 in FIG.13A.

In FIG. 13B, since the PDSCH of PCell is specified by the PDCCH, PUCCHresources (PUCCH Format 1b resources) associated in a one-to-onecorrespondence with the beginning CCE index n_(CCE) of the CCE occupiedby the PDCCH are instructed. The PDSCHs of SCell1 and SCell2 are alsospecified by the PDCCH, and ARI (ARI1) is indicated to the TPC field bythe PDCCH that specifies the PDSCHs. Terminal 200 determines which oneof the four previously set PUCCH resources (PUCCH Format 3 resources) isto be used for PUCCH transmission according to the ARI (ARI1) indicatedby the PDCCH. Moreover, the PDSCHs of SCell3 and SCell4 are specified bythe ePDCCH and ARI (ARI2) is indicated to the TPC field by the ePDCCHthat specifies the PDSCHs. Terminal 200 determines which one of the fourpreviously set PUCCH resources (PUCCH Format 3 resources) is to be usedfor PUCCH transmission according to the ARI (ARI2) indicated by theePDCCH.

In FIG. 13C, since the PDSCHs of PCell, SCell1 and SCell4 are specifiedby an ePDCCH, ARI is indicated to the TPC field (ARI3 is indicated toPCell and ARI2 is indicated to SCell1 and SCell4) by the ePDCCH thatspecifies the PDSCHs. ARI2 and ARI3 are always used as having the samevalue. Furthermore, the four previously set PUCCH resources are commonso that PUCCH resources specified by ARI2 and ARI3 also becomeidentical. Terminal 200 determines which one of the four previously setPUCCH resources (PUCCH Format 3 resources) is to be used for PUCCHtransmission according to the ARI (ARI2=ARI3) indicated by the ePDCCH.On the other hand, the PDSCHs of SCell2 and SCell3 are specified by thePDCCH and ARI (ARI1) is indicated to the TPC field by the PDCCH thatspecifies the PDSCHs. Terminal 200 determines which one of the fourpreviously set PUCCH resources (PUCCH Format 3 resources) is to be usedfor PUCCH transmission according to the ARI (ARI1) indicated by thePDCCH.

According to FIG. 13B and FIG. 13C, the PUCCH resources determined byARI1 and the PUCCH resources determined by ARI2 (=ARI3) are usedindependently of each other, and therefore when two ARIs are indicatedto terminal 200, it is necessary to determine ARI that specifies PUCCHresources to be used. As an example, in FIG. 13B, when ARI indicated bya PDCCH (ARI1) is always given priority, base station 100 expects toreceive a response signal by a PUCCH resource determined by ARI1.However, when terminal 200 fails to receive a PDCCH that specifies bothPDSCHs of SCell1 and SCell2, terminal 200 cannot receive ARI1. Instead,terminal 200 transmits a response signal using PUCCH resourcesdetermined by ARI indicated by the ePDCCH (ARI2) that specifies thePDSCHs of SCell3 and SCell4. Therefore, base station 100 is to assumereception of a response signal by PUCCH resources determined by ARI2 aswell. That is, base station 100 is to secure two PUCCH resources (PUCCHFormat 3 resources) intended for one terminal, which results in anincrease of PUCCH overhead.

The method of indicating PUCCH resources according to the presentembodiment is a method of determining PUCCH resources that prevents suchPUCCH overhead from increasing. The method will be described withreference to FIGS. 14A to 14C.

In FIG. 14B, since the PDSCH of PCell is specified by the PDCCH, PUCCHresources (PUCCH Format 1b resources) associated in a one-to-onecorrespondence with the beginning CCE index n_(CCE) of the CCE occupiedby the PDCCH are specified. The PDSCHs of SCell1 and SCell2 are alsospecified by a PDCCH, and ARI (ARI1) is indicated to the TPC field bythe PDCCH that specifies the PDSCHs. Furthermore, the PDSCHs of SCell3and SCell4 are specified by an ePDCCH and ARI (ARI2) is indicated to theTPC field by the PDCCH that specifies the PDSCHs. In the presentembodiment, ARI1 and ARI2 are always used as having the same value.Furthermore, the four previously set PUCCH resources are common so thatPUCCH resources specified by ARI1 and ARI2 also become identical.Terminal 200 determines which one of the four previously set PUCCHresources (PUCCH Format 3 resources) is to be used for PUCCHtransmission according to ARI (ARI1=ARI2) indicated by the PDCCH orePDCCH.

In FIG. 14C, since the PDSCHs of PCell, SCell1 and SCell4 are specifiedby an ePDCCH, ARI is indicated to the TPC field (ARI3 is indicated toPCell, ARI2 is specified to SCell1 and SCell4) by the ePDCCH thatspecifies the PDSCHs. Furthermore, the PDSCHs of SCell2 and SCell3 arespecified by a PDCCH and ARI (ARI1) is indicated to the TPC field by thePDCCH that specifies the PDSCHs. In the present embodiment, ARIL ARI2and ARI3 are always used as having the same value. Furthermore, the fourpreviously set PUCCH resources are common so that PUCCH resourcesspecified by ARIL ARI2 and ARI3 also become identical. Terminal 200determines which one of the four previously set PUCCH resources (PUCCHFormat 3 resources) is to be used for PUCCH transmission according toARI (ARI1=ARI2=ARI3) specified by the PDCCH or ePDCCH.

As described above, according to the present embodiment, when carrieraggregation is set in a case where a PDCCH and ePDCCH are used incombination, ARI2 and ARI3 are used as having the same value, and inaddition, ARI1 is also used as having the same value as ARI2 and ARI3.Moreover, the four previously set PUCCH resources are made to be commonso that PUCCH resources specified by ARIL ARI2 and ARI3 also becomeidentical. It is thereby possible to prevent PUCCH overhead fromincreasing when a PDCCH and ePDCCH are used in combination.

Note that when carrier aggregation is set, if a PDSCH is assigned toonly PCell, PUCCH Format 1b resources may be used which are PUCCHresources optimized to the number of bits of a fewer results of errordetection in the same way as when carrier aggregation is not set byspecifying the PDSCHs not by ePDCCH but by PDCCH as in the case ofEmbodiment 2.

Embodiment 4

In the present embodiment, a description will be given of, inassociation with Embodiment 3, a method of indicating PUCCH resourceswhen a PDCCH and ePDCCH are used in combination for each cell, andcarrier aggregation and channel selection are set in terminal 200.

In the present embodiment, PDCCH and ePDCCH are used in combination foreach cell or subframe as shown in FIG. 15A. For example, in subframe #0(SF #0) in FIG. 15A, base station 100 uses the PDCCH to specify thePDSCH in PCell and uses the ePDCCH to specify the PDSCH in SCell. FIG.15B shows the method of determining PUCCH resources in subframe #0 inFIG. 15A, FIG. 15C shows the method of determining PUCCH resources insubframe #1 in FIG. 15A, and FIG. 15D shows the method of determiningPUCCH resources in subframe #2 in FIG. 15A.

In FIG. 15C, since the PDSCH of PCell is specified by an ePDCCH, ARI(ARI3) is specified to the TPC field by the ePDCCH that specifies thePDSCH. Furthermore, the PDSCH of SCell is specified by the PDCCH and ARI(ARI1) is specified to the TPC field by PDCCH that specifies the PDSCH.According to Embodiment 3, ARI1 and ARI3 are always used as having thesame value. Furthermore, previously set PUCCH resources are common sothat PUCCH resources specified by ARI1 and ARI3 also become identical.Terminal 200 determines which one of the four previously set PUCCHresource sets (PUCCH Format 1b resource set), each including fourresources is to be used for PUCCH transmission according to ARI(ARI1=ARI3) specified by the PDCCH.

In FIG. 15D, since the PDSCH of PCell is specified by the ePDCCH, ARI(ARI3) is specified to the TPC field by the ePDCCH that specifies thePDSCH. Furthermore, the PDSCH of SCell is also specified by the ePDCCHand ARI (ARI2) is indicated to the TPC field by the ePDCCH thatspecifies the PDSCH. According to Embodiment 3, ARI2 and ARI3 are alwaysused as having the same value. Moreover, previously set PUCCH resourcesare common so that PUCCH resources specified by ARI2 and ARI3 alsobecome identical. Terminal 200 determine which one of the fourpreviously set PUCCH resource sets (PUCCH Format 1b resource sets) eachincluding four resources is to be used for PUCCH transmission accordingto ARI (ARI2=ARI3) specified by the PDCCH.

With respect to FIG. 15B, the result is similar to FIG. 15C and FIG.15D. Since the PDSCH of PCell is specified by the PDCCH, PUCCH resources(PUCCH Format 1b resources) associated in a one-to-one correspondencewith the beginning CCE index n_(CCE) of the CCE occupied by the PDCCHand the next index are specified. Moreover, the PDSCH of SCell isspecified by the ePDCCH and ARI (ARI2) is indicated to the TPC field byePDCCH that specifies the PDSCH. Terminal 200 determines which one ofthe four previously set PUCCH resource sets (PUCCH Format 1b resourcesets) each including four resources is to be used for PUCCH transmissionaccording to ARI (ARI2) indicated by the ePDCCH.

Since, in FIG. 15D, ARI2 specifies which one of the four previously setPUCCH resource sets (PUCCH Format 1b resource sets) is to be used forPUCCH transmission, in FIG. 15B, ARI2 also specifies which one of thefour previously set PUCCH resource sets (PUCCH Format 1b resource sets)is to be used for PUCCH transmission. On the other hand, in FIG. 15B,PUCCH resources corresponding to the beginning CCE index n_(CCE) and thenext n_(CCE)+1 of PDCCH that specifies the PDSCH of PCell are specified.Thus, in FIG. 15B, six PUCCH resources in total are specified, and it isnecessary to determine which four resources are used. Particularly, asan example, PUCCH resources corresponding to n_(CCE) and the nextn_(CCE)+1 are given priority in FIG. 15B, base station 100 expects toreceive a response signal using the PUCCH resources assuming PUCCHresources 0 and 1. However, upon failing to receive a PDCCH thatspecifies the PDSCH of PCell, terminal 200 transmits a response signalusing PUCCH resources 0 and 1 (and 2 and 3) determined by ARI (ARI2)instructed by ePDCCH that specifies the PDSCH of SCell. Therefore, basestation 100 is to assume reception of a response signal using PUCCHresources 0 and 1 determined by ARI2. That is, base station 100 is tosecure six PUCCH resources (PUCCH Format 1b resources) for one terminal,which results in an increase of PUCCH overhead.

Thus, the method of indicating PUCCH resources according to the presentembodiment is a method of determining PUCCH resources that preventsPUCCH overhead from increasing. The method will be described withreference to FIGS. 16A to 16D.

In FIG. 16C, since the PDSCH of PCell is specified by the ePDCCH, ARI(ARI3) is indicated to the TPC field by the ePDCCH that specifies thePDSCH. Terminal 200 determines which one of the four previously setPUCCH resource sets (PUCCH Format 1b resource sets) each including tworesources is to be used for PUCCH transmission according to ARI (ARI3)indicated by the ePDCCH. Furthermore, the PDSCH of SCell is specified bythe PDCCH and ARI (ARI1) is indicated to the TPC field by PDCCH thatspecifies the PDSCH. Terminal 200 determines which one of the fourpreviously set PUCCH resource sets (PUCCH Format 1b resource sets) eachincluding two resources is to be used for PUCCH transmission accordingto ARI (ARI1) indicated by the PDCCH. Terminal 200 determines PUCCHresources that indicate response signals from among the four PUCCHresources obtained above based on a combination of results of errordetection.

In FIG. 16D, since the PDSCH of PCell is specified by the ePDCCH, ARI(ARI3) is indicated to the TPC field by the ePDCCH that specifies thePDSCH. Terminal 200 determines which one of the four previously setPUCCH resource sets (PUCCH Format 1b resource sets) each including tworesources is to be used for PUCCH transmission according to ARI (ARI3)indicated by the ePDCCH. Furthermore, the PDSCH of SCell is alsospecified by the ePDCCH and ARI (ARI2) is indicated to the TPC field bythe ePDCCH that specifies the PDSCH. Terminal 200 determines which oneof the four previously set PUCCH resource sets (PUCCH Format 1b resourcesets) each including two resources is to be used for PUCCH transmissionaccording to ARI (ARI2) indicated by the ePDCCH. Terminal 200 determinesPUCCH resources that indicate a response signal from among the fourPUCCH resources obtained above based on a combination of results oferror detection.

In FIG. 16B, since the PDSCH of PCell is specified by the PDCCH, PUCCHresources (PUCCH Format 1b resources) associated in a one-to-onecorrespondence with the beginning CCE index n_(CCE) and the next CCEindex of the CCE occupied by the PDCCH are specified. Furthermore, thePDSCH of SCell is specified by ePDCCH and ARI (ARI2) is indicated to theTPC field by the ePDCCH that specifies the PDSCH. Terminal 200determines which one of the four previously set PUCCH resource sets(PUCCH Format 1b resource sets) each including two resources is to beused for PUCCH transmission according to ARI (ARI2) indicated by theePDCCH. Terminal 200 determines a PUCCH resource for indicating aresponse signal from among the four PUCCH resources obtained above basedon a combination of results of error detection.

As described above, according to the present embodiment, when channelselection is set, in a case where a PDCCH and ePDCCH are used incombination, ARI1 and ARI3, and PUCCH resources instructed by therespective ARIs are used independently. Furthermore, ARI2 and ARI3, andPUCCH resources instructed by the respective ARIs are usedindependently. It is thereby possible to prevent PUCCH overhead fromincreasing when a PDCCH and ePDCCH are operated in combination.

Note that since channel selection supports only two cells, ARI1 and ARI2will not be simultaneously indicated. For this reason, previously setPUCCH resources may be set for ARI1 and ARI2 independently or may be setcommonly. When PUCCH resources are set commonly, signaling of PUCCHresources can be made common for ARI1 and ARI2, and therefore signalingcan be reduced.

Embodiments 1 to 4 have been described thus far.

The above description assumes that ARI is indicated to the TPC field,but the present invention is not limited to this, and a TPC command maybe indicated to the TPC field and ARI may be further indicated todifferent fields within the same DL assignment (PDCCH or ePDCCH thatspecifies PDSCH). In short, ARI is to be indicated within DL assignment(PDSCH or ePDCCH that specifies PDCCH).

The functional blocks used in the embodiments described above may beimplemented by software to be executed by a computer or may beimplemented by software in concert with hardware.

The functional blocks described in the embodiments described above areachieved by an LSI, which is typically an integrated circuit. Thefunctional blocks may be provided as individual chips, or part or all ofthe functional blocks may be provided as a single chip. Depending on thelevel of integration, the LSI may be referred to as an IC, a system LSI,a super LSI, or an ultra LSI.

In addition, the circuit integration is not limited to LSI and may beachieved by dedicated circuitry or a general-purpose processor otherthan an LSI. After fabrication of LSI, a field programmable gate array(FPGA), which is programmable, or a reconfigurable processor whichallows reconfiguration of connections and settings of circuit cells inLSI may be used.

Should a circuit integration technology replacing LSI appear as a resultof advancements in semiconductor technology or other technologiesderived from the technology, the functional blocks could be integratedusing such a technology. Another possibility is the application ofbiotechnology and/or the like.

A terminal apparatus according to this disclosure is a terminalapparatus that communicates with a base station apparatus using aplurality of component carriers and that receives a downlink controlsignal in a first resource region usable for both a downlink controlchannel and a downlink data channel or a second resource region usablefor a downlink control channel, the terminal apparatus including: adownlink control signal detection section that detects a downlinkcontrol signal assigned to the first resource region or the secondresource region, for each of the component carriers; a receiving sectionthat receives downlink data items using the plurality of componentcarriers, respectively; an error detection section that detects an errorof each of the downlink data items; a generating section that generatesa response signals using a result of error detection on each of thedownlink data items, the result of error detection being obtained by theerror detection section; and a control section that transmits theresponse signal to the base station apparatus, in which the controlsection switches between resource regions of an uplink communicationcontrol channel for transmitting the response signal, in accordance withwhether the downlink control signal detection section detects thedownlink control signal in the first resource region or the secondresource region.

In the terminal apparatus according to this disclosure, the controlsection switches between the resource regions of the uplink controlchannel for transmitting the response signal when the downlink controlsignal detection section detects a downlink control signal in only thesecond resource region of a primary cell (PCell) and when the downlinkcontrol signal detection section detects a downlink control signal inany region at least other than the second resource region of the PCell.

A transmission method according to this disclosure is a transmissionmethod for a terminal apparatus that communicates with a base stationapparatus using a plurality of component carriers and that receives adownlink control signal in a first resource region usable for both adownlink control channel and a downlink data channel or a secondresource region usable for a downlink control channel, the transmissionmethod including: detecting a downlink control signal assigned to thefirst resource region or the second resource region, for each of thecomponent carriers; receiving downlink data items using the plurality ofcomponent carriers, respectively; detecting an error of each of thedownlink data items; generating a response signal using an obtainedresult of error detection on each of the downlink data items; andtransmitting the response signal to the base station apparatus, in whichswitching between resource regions of an uplink communication controlchannel for transmitting the response signal is performed in accordancewith whether the downlink control signal is detected in the firstresource region or the second resource region.

The disclosure of Japanese Patent Application No. 2012-109502, filed onMay 11, 2012, including the specification, drawings and abstract isincorporated herein by reference in its entirety.

INDUSTRIAL APPLICABILITY

The present invention is suitable for use in a mobile communicationsystem or the like.

REFERENCE SIGNS LIST

-   -   100 Base station    -   200 Terminal    -   101, 208 Control section    -   102 Control information generating section    -   103, 105 Coding section    -   104, 107 Modulation section    -   106 Data transmission controlling section    -   108 Mapping section    -   109, 218 IFFT section    -   110, 219 CP adding section    -   111, 222 Radio transmitting section    -   112, 201 Radio receiving section    -   113, 202 CP removing section    -   114 PUCCH extracting section    -   115 Despreading section    -   116 Sequence control section    -   117 Correlation processing section    -   118 A/N determining section    -   119 Bundled A/N despreading section    -   120 IDFT section    -   121 Bundled A/N determining section    -   122 Retransmission control signal generating section    -   203 FFT section    -   204 Extraction section    -   205, 209 Demodulation section    -   206, 210 Decoding section    -   207 Determination section    -   211 CRC section    -   212 Response signal generating section    -   213 Coding and modulation section    -   214 Primary-spreading section    -   215 Secondary-spreading section    -   216 DFT section    -   217 Spreading section    -   220 Time-multiplexing section    -   221 Selection section

The invention claimed is:
 1. A system including: a base stationcomprising: a first transmitter, which, in operation, transmits a firstdownlink control channel signal in an enhanced Physical Downlink ControlChannel (ePDCCH) and transmits a second downlink control channel signalin a Physical Downlink Control Channel (PDCCH), wherein the firstdownlink control channel signal indicates a first downlink datatransmission on a secondary cell (SCell) and the second downlink controlchannel signal indicates a second downlink data transmission on anotherSCell; and a first receiver, which, in operation, receives a responsesignal in a physical uplink control channel (PUCCH) resourcecorresponding to a PUCCH resource value, wherein the PUCCH resourcevalue corresponds to at least one of a first indicator value transmittedin the ePDCCH and a second indicator value transmitted in the PDCCH,wherein the first indicator value and the second indicator value areidentical and denote a common PUCCH resource; and a terminal apparatuscomprising: a second receiver, which, in operation, receives the firstdownlink control channel signal and receives the second downlink controlchannel signal; a controller, which, in operation, determines the PUCCHresource value based on at least one of the first indicator valuereceived in the ePDCCH and the second indicator value received in thePDCCH; and a second transmitter, which, in operation, transmits theresponse signal using the determined PUCCH resource.
 2. The systemaccording to claim 1, wherein the first indicator value and the secondindicator value are in Transmit Power Control (TPC) fields of the firstand second downlink control channel signals transmitted in the ePDCCHand the PDCCH.
 3. The system according to claim 1, wherein the PUCCHresource value is selected from a set of PUCCH resource values.
 4. Thesystem according to claim 3, wherein the set of PUCCH resource valuesincludes four PUCCH resource values.
 5. A communication methodimplemented by a base station and a terminal apparatus, comprising:transmitting, from the base station to the terminal apparatus, a firstdownlink control channel signal in an enhanced Physical Downlink ControlChannel (ePDCCH) and a second downlink control channel signal in aPhysical Downlink Control Channel (PDCCH), wherein the first downlinkcontrol channel signal indicates a first downlink data transmission on asecondary cell (SCell) and the second downlink control channel signalindicates a second downlink data transmission on another SCell;determining, at the terminal apparatus, a physical uplink controlchannel (PUCCH) resource corresponding to a PUCCH resource value,wherein the PUCCH resource value corresponds to at least one of a firstindicator value transmitted in the ePDCCH and a second indicator valuetransmitted in the PDCCH, wherein the first indicator value and thesecond indicator value are identical and denote a common PUCCH resource;and transmitting, from the terminal apparatus to the base station, aresponse signal using the determined PUCCH resource.
 6. Thecommunication method according to claim 5, wherein the first indicatorvalue and the second indicator value are in Transmit Power Control (TPC)fields of the first and second downlink control channel signalstransmitted in the ePDCCH and the PDCCH.
 7. The communication methodaccording to claim 5, wherein the PUCCH resource value is selected froma set of PUCCH resource values.
 8. The communication method according toclaim 7, wherein the set of PUCCH resource values includes four PUCCHresource values.